title: Effects of tubing length and coupling method on hearing threshold and real-ear to coupler difference measures.
abstract: OBJECTIVE
  This tutorial demonstrates the effects of tubing length and coupling type (i.e., foam tip or personal earmold) on hearing threshold and real-ear-to-coupler difference (RECD) measures.
  
  
  METHODS
  Hearing thresholds from 0.25 kHz through 8 kHz are reported at various tubing lengths for 28 normal-hearing adults between the ages of 22 and 31 years. RECD values are reported for 14 of the adults. All measures were made with an insert earphone coupled to a standard foam tip and with an insert earphone coupled to each participant's personal earmold.
  
  
  RESULTS
  Threshold and RECD measures obtained with a personal earmold were significantly different from those obtained with a foam tip on repeated measures analyses of variance. One-sample t tests showed these differences to vary systematically with increasing tubing length, with the largest average differences (7-8 dB) occurring at 4 kHz.
  
  
  CONCLUSIONS
  This systematic examination demonstrates the equal and opposite effects of tubing length on threshold and acoustic measures. Specifically, as tubing length increased, sound pressure level in the ear canal decreased, affecting both hearing thresholds and the real-ear portion of the RECDs. This demonstration shows that when the same coupling method is used to obtain the hearing thresholds and RECD, equal and accurate estimates of real-ear sound pressure level are obtained.
authors.affiliation: Arizona State University, Tempe, USA. samantha.gustafson@vanderbilt.edu
authors.forename: Samantha
authors.initials: S
authors.lastname: Gustafson
authors.forename: Andrea
authors.initials: A
authors.lastname: Pittman
authors.forename: Robert
authors.initials: R
authors.lastname: Fanning
mesh_terms: D000328:Adult; D001299:Audiometry / Q000295:instrumentation / Q000379:methods*; D001309:Auditory Threshold / Q000502:physiology*; D005260:Female; D006310:Hearing Aids; D006801:Humans; D008297:Male; D017755:Prosthesis Fitting / Q000295:instrumentation / Q000379:methods; D012016:Reference Values; D055815:Young Adult
keywords: audiometry; earmolds; real-ear measures